1. Field of the Invention
The invention generally relates to textured multi-component yarns having increased elasticity and recovery, and processes for their production. More specifically, the invention relates to multi-component yarns having a polybutylene terephthalate component and a component of another thermoplastic material, and having good physical and aesthetic properties along with improved elasticity and recovery, and processes for their production.
2. Description of the Prior Art
Fabrics woven from synthetic yarns such as those made from textured polyethylene terephthalate (PET) are commonly used in many applications, due in part to their strength and durability. The types of yarns used are selected to achieve the desired properties for the intended end use. For example, air jet textured yarns are often utilized because of the ease with which they can be produced. One disadvantage of fabrics made from air jet textured PET yarns is that they generally have limited elasticity/recovery capability. This becomes particularly apparent when the fabric woven from such yarns is used to cover an irregularly-shaped article. For example, when fabrics woven from conventional bulk PET yarns are to be used to cover items such as automotive seating, it can be difficult to get a close fit of the fabric without extensive labor input to custom-fit the fabric to the seat. As a result, such fabrics can tend to pucker and gap, thereby causing a reduced quality appearance. Furthermore, since such seating is generally cushioned, it often results that the fabric is worn undesirably as a result of its inability to stretch and recover when the cushioned seating is compressed, as when someone sits on it.
Attempts have been made to increase the elasticity of air jet textured PET yarns used in woven fabrics; however, such attempts typically have involved increasing the amount of shrinkage in the yarns, since an increase in elasticity and recovery generally accompanies an increase in shrinkage. However, increasing the shrinkage in the yarn end product can be particularly difficult when it is desired that the yarns are to be colored. In processes where the PET yarns are package dyed, the heating stage of the dye process tends to virtually eliminate the ability of the yarns to shrink. As a result, the package-dyed air jet textured PET yarns generally have little to no elasticity or recovery capability.
The other option generally available for obtaining dyed PET yarns having some elasticity is by solution dyeing the yarns (i.e., introducing polymer pigments or insoluble dyes into the polymer melt or spinning solution prior to extrusion), and false twist texturing them, since false twisting generally produces yarns having high levels of shrinkage. Because the color is therefore inherent in the yarn prior to texturizing, the elastic properties of the yarn can be retained. However, because the yarns retain a relatively high level of shrinkage, when fabrics woven from the solution-dyed false-twist textured PET yarns are subjected to heat during fabric finishing processes, they have a tendency to shrink, leading to significant yield losses and quality problems in the end product.
Another attempt for increasing the stretchability of PET fibers is described in U.S. Pat. No. 4,755,336 to Deeg, et al. This patent describes a process for melt spinning a blend of about 5 to 25% by weight of polyethylene terephthalate (PET) with polybutylene terephthalate (PBT), to produce a yarn having increased stretchability. As described in the patent, the fibers are drawn at an elevated temperature following extrusion to induce a specific form of crystal. The yarns are then subjected to a heat relaxation treatment which changes the crystal form of the polybutylene terephthalate to add shrinkage, thereby causing the fibers to have an increased degree of stretchability. Because the polybutylene terephthalate and polyethylene terephthalate are mixed while in their molten form, the resulting yarns would have properties which are essentially a compromise between the properties of the two material inputs, and thus which would differ from the physical and aesthetic properties of the all-PET yarns. In addition, because the elasticity is increased by increasing yarn shrinkage, the problem of yield loss would still exist when the yarns are converted to a finished product. Furthermore, the large majority of the material input is PBT, and because PBT is generally more expensive than PET, the yarns discussed in the Deeg, et al. patent would tend to be significantly more expensive than the all-PET yarns.
Thus, a need exists for yarns which can be used in the production of woven fabrics which have a good degree of elasticity and recovery, along with good physical and aesthetic properties. In addition, a need exists for yarns which can be used in the production of woven fabrics having increased elasticity and recovery, at set levels of shrinkage.
The instant invention overcomes the deficiencies of the prior art by providing bulk yarns having high elastic recovery and superior elasticity, while also providing superior color, hand and appearance characteristics.
In addition, certain embodiments of the invention provide increased elasticity and recovery along with low shrinkage. This is surprising because the characteristics of high elasticity and recovery and low shrinkage are typically at odds with each other. As a result, the yarns of these embodiments of the instant invention enable the production of superior fabrics having improved elasticity and recovery, which would be expected to enable the fabrics to more readily conform to irregularly-shaped articles such as automotive seating.
The yarns of the first embodiment of the invention are achieved by providing solution-dyed polybutylene terephthalate (PBT) filaments and filaments of a different thermoplastic polymer (e.g., polyethylene terephthalate (PET) or nylon) to an air jet texturizer to form a core-bulked yarn, where the PBT filaments form the core and the filaments of the other polymer form a coiled or looped effect yarn about the PBT core.
The PBT material is desirably combined with organic and/or inorganic pigments while it is in a flowable form (e.g., molten), to provide a colored PBT material. This material is then spun into a plurality of polymer material streams using a conventional melt spinning operation, and the streams are then quenched to at least partially solidify the streams into a plurality of solution-dyed PBT filaments. Because the dyeing occurs during the spinning process, the disadvantages associated with package dyeing (e.g., problems of dye bath disposal without adverse environmental impact, etc.) can be avoided.
The individual filaments are gathered into a bundle, and wound under tension to form a PBT yarn structure. Preferably, the filaments are also intermingled during the gathering process such as through the use of an interlacing jet, so that the filaments form a cohesive bundle.
The thus-produced solution-dyed multifilament PBT yarn is then fed to an air jet texturizer along with another multifilament yarn of a different thermoplastic material, which is selected to provide the composite yarn with specific physical and aesthetic characteristics. For example, the other multifilament yarn can be a polyester or nylon multifilament yarn, since these fibers provide good strength, hand and appearance, yet are relatively inexpensive. The second yarn component is also desirably solution-dyed to the same color as the PBT component, although the component could be provided as different color(s) depending on the choice of the manufacturer.
The PBT component and the other yarn component are desirably each individually fed through separate drawing arrangements, in order that each of the respective yarn components can be drawn to its preferred optimal draw ratio. For example, where the second component is formed from PET, the PBT component may desirably be drawn at a lower draw ratio than the PET component. The respective drawing arrangements desirably utilize a plurality of heated rollers, to facilitate in the drawing and heat setting of the yarns.
The two yarn components are then fed to an air jet texturizer to form a core-bulked yarn structure, with the PBT component representing the core of the composite yarn. In other words, the feeding arrangement is such that the PBT yarn establishes itself as the core component while the second yarn component forms a plurality of coils and loops extending outwardly from the PBT core. For example, the PBT yarn can be fed to the air jet texturizer at a slower rate than the other component, and/or the PBT component can be guided through a liquid bath prior to entry into the air jet.
Because the aesthetic characteristics of the thus-produced yarns are predominantly dictated by the effect yarn, the yarns therefore appear substantially the same as those made entirely from the effect yarn material. However, the multicomponent yarns have been found to have greater elasticity and recovery than is achieved by those formed entirely from the effect yarn material, at the same levels of shrinkage. Stated differently, yarns at the same levels of elasticity and recovery as prior art yarns would have lower levels of shrinkage, and thus smaller yield losses. As a result, the multicomponent yarns can be used to produce fabrics having a good degree of elasticity and recovery, and a low level of shrinkage, which means that the fabrics do not experience the yield losses commonly experienced with the prior art fabrics.
A second embodiment of the invention involves the production of multicomponent yarns by false-twist texturing as individual threadlines each of a PBT yarn component and a multifilament yarn component of another thermoplastic material (e.g., PET or nylon), then combining the two yarn components using an air entanglement jet. Because the natural draw ratios of the PBT component and the other yarn component are different, the process also involves drawing each of the yarn components during the texturing process using different draw ratios for each. Although the thus-produced yarns retain some shrinkage (particularly due to their false-twisted nature), they have an enhanced level of elasticity and recovery, and good strength and aesthetic characteristics. As a result, they are particularly usefuel in the production of woven fabrics having a high degree of elasticity and recovery along with good hand and appearance.